In the case of a one half horsepower capacity cooler, the water consumption exceeds 15 liters per hour. In such water evaporative cooling systems, large quantities of salts may accumulate due to the evaporation of water all through the working hours of the cooler. The cooling efficiency of the cooler declines due to the increased concentration of salts which form solid salt crystals that spread and multiply from inside to outside the cooler. The accumulated salt plugs air openings and damages the water evaporation mat (which is typically made of straw). This necessitates frequent changing of the water evaporation mats. The salts also contribute to rapid corrosion of the cooler frame and its metallic parts and generates offensive odors.
In order to avoid the harmful effect of the salts and in order to maintain the air conditioner cooler capacity, the cooling water must be changed regularly based upon the cooler's hours of operation, typically every month. This is accomplished by decanting salty water from the cooler reservoir and refilling same with fresh water from a flow control spigot. Typically, ordinary tap water is used. It is difficult to remember to do this job in the recommended time interval. Also it is difficult to perform this task when the cooler is mounted in a high location such as a facade or upper surface of a building.
Therefore, most of the air conditioner salty water might not be changed until it looses its cooling capability and damages the evaporation mat. Once this occurs, a thorough cleaning must be carried out together with replacement of the mat and other maintenance which is necessitated by the salt's harmful effect on the cooler frame and metallic parts.
These draw backs are unfortunate because evaporate air conditioners consume less electric power than other types of air conditioners. The need for frequent maintenance and cleaning due to salt build up in evaporative air conditioner systems has been a limiting factor in the commercial acceptance.